1. Field of the Invention
The present invention relates to a bar extruding implement for extruding, when needed, a bar that wears down gradually, such as a black or color lead for a mechanical pencil, a crayon, an erasing rubber, a lipstick or a stick for an eyebrow pencil, capable of automatically ejecting a marginal portion of the bar, i.e., a loss portion unavoidably left unused in the bar extruding implement.
2. Description of the Related Art
Referring to FIG. 1 showing a previously proposed color lead extruding implement, i.e., a bar extruding implement, for extruding a colored lead of, for example, a colored pencil, the color lead extruding implement comprises a barrel 1, a rotational operating head 2 rotatably fitted in the rear end of the barrel 1, a helically wound wire 3 having a base end fixedly wound around the inner end of the rotational operating head 2 and inserted in the barrel 1, a color lead holding member 4 holding a color lead at its rear end, and inserted in and interlocked with the helically wound wire 3, and a barrel cap 5 screwed in the front end of the barrel 1 provided with an internal screw thread 1a. The rotational operating head 2 is provided with an annular protrusion 2a fitted in an annular groove 1c formed in the inner surface of the barrel 1 to restrain the rotational operating head 2 from falling off the barrel 1. The color lead holding member 4 has a projection 4a in engagement with a longitudinal guide groove 1b formed in the inner surface of the barrel 1 to restrain the color lead holding member 4 from turning, and three protrusions 4b extending between the coils of the helically wound wire 3. When the rotational operating head 2 is turned in one direction, the color lead holding member 4 is moved axially toward the front end of the barrel 1 by the helically wound wire 3, so that the color lead is extruded gradually from the tip of the barrel cap 5 attached to the front end of the barrel 1 as the rotational operating head 2 is turned. When the rotational operating head 2 is turned in the opposite direction, the color lead is retracted into the barrel.
The barrel 1 must be provided with the internal screw thread 1a in its front end, the longitudinal guide groove 1b for guiding the color lead holding member 4, and the annular groove 1c for receiving the annular protrusion 2a of the rotational operating head 2. Consequently, the color lead extruding implement has a complex construction and requires much assembling time. Since the coils of the helically wound wire 3 are liable to be formed at irregular pitches, the color lead cannot be smoothly extruded. Furthermore, when the color lead is worn out and only the marginal portion of the color lead is left on the color lead holding member 4, it is difficult to remove the marginal portion of the color lead from the color lead extruding implement in replacing the marginal portion of the color lead with a new color lead.